Between 27 and 29 April 1915, Turkish counter-attacks attempted unsuccessfully to drive the Anzacs off the Gallipoli peninsula. The small area of the Gallipoli peninsula that they now held became known as Anzac. The area on the southern tip of the peninsula, captured by British units on 25 April, became known as Helles.

Sources:
http://www.anzacsite.gov.au/5environment/timelines/australia-gallipoli-campaign/january-april-1915.html